EKG Week 1

S Wave
• Negative waveform that
follows R wave
• Usually negative Ü
• R & S waves represent
depolarization of Left &
Right ventricles
• Ventricular Enlargement-
➢RV = big R wave
➢LV = big S wave
ST Segment
• Starts at end of QRS
complex & ends at
beginning of T wave
• Point where S wave &
ST segment meet is
called the “J point”
• Normally isoelectric
(flat) in the limb leads,
but usually not more
than 1 mm Ó or Ô
in any lead
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J Point
• Used to
measure ST Ó
or Ô
• Find J point,
• Go right 1 small
box,
• Count down #
of sm. boxes to
baseline
(3.5mm STÓ)
ST Segment Displacement
• Use PR segment to assess degree of elevation or
depression of the ST segment from baseline
• Measure over one small box after the J point &
count number of boxes down/up to baseline
• ST elevated if segment 1 mm > above baseline
• ST depressed if segment 1mm > below baseline
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